<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        html {
            /*如果html设置了背景色 body的背景色就不会填充*/
            background-color: blue;
        }
        /*body的背景色 会充满*/

        body {
            background-color: gold;
        }
    </style>
</head>

<body>

    <div>
        fdskjdlka <br> fdskjdlka <br> fdskjdlka <br> fdskjdlka <br>
    </div>

</body>

</html>